1. Field of the Invention
This invention relates to a supramolecular-structured bio-degradable polymeric assembly with biodegradable moieties at both terminals in the body of the subject.
2. Related Background Art
Of known biodegradable polymers, attention has been paid by researchers on hydrophilic/water soluble polymers designed to effectively deliver drugs linked with covalent and/or ion bonds thereof and hydrophobic polymers that gradually release drugs dissolved or dispersed therein as a result of biodegradation.
While in the former case drug molecules are linked to the polymeric backbones via biodegradable spacer to be in target cells or tissues by enzymatic hydrolysis of the spacers, the chains of such polymers become less soluble or apt to be blocked from accessing hydrolytic enzymes by steric hindrance to consequently reduce their biodegradability if the incorporation of drugs into the polymer is enhanced. The drugs have to be linked with polymeric chains in a manner that is easy both in binding them together and in releasing them from each other by biodegradation and, at the same time, does not damage their activities. In practice, these requirements poses a number of problems to be solved in finding a method of appropriately introducing a drug into polymers.
In the case of polymers of the latter group, they are designed to release the drugs dissolved or dispersed therein by their degradation. In order to achieve degradation-controlled drug release, the drug has to be prevented from undesirable leakage during storage or before the biodegradation of the polymer and, at the same time, the biodegradation of the polymer has to be so control led that the hydrolysis of the polymer takes place only via the surface front.
Normally, biodegradation of a substance occurs via either enzymatic or non-enzymatic hydrolysis. Therefore, from the view point of controlling the rates at both water intrusion and hydrolysis, the substance is inevitably made hydrophobic to reduce the former rate and the biodegradability of the biodegradable groups of the substance is raised to increase the latter rate. These operations for pharmaceutical formulation, however, by turn make the carrier less stable and storable and limit the scope of pharmaceutical applicability and applicable sites of the body.
In short, with known technologies, it is practically impossible to bind a drug to and unbind it from polymer chains in a controlled manner and release the drug into the subject at intended sites at an intended rate. Under these circumstances, there is a strong demand for a novel and highly water soluble polymer that can be used as a carrier for a variety of drugs and is designed to carry a drug and release it at any desired rate and also for a novel hydrophilic gel (hydrogel) that can release the drug it carries in response to a specific biodegradation process observable only in patients.
It is therefore an object of the present invention to provide a supramolecular-structured biodegradable polymeric assembly designed to deliver a drug at an enhanced rate to intended release sites in a highly efficient and reliable way so as to exhibit non-linear (pulse-like) drug release into cells or tissues of the patient.